If by not family oriented you mean you want a quiet and mellow resort I would say the Ritz would be a good bet. It is on the nicest beach in greater San Juan and is probably the quietest upscale resort in the area. Though it is a little removed from the main Isla Verde area, it's only a short walk to restaurants and the other livelier resorts. Definitely a cab ride to other areas of San Juan. Puerto Rico in general is very family friendly so pretty much wherever you go there will probably be at least a few kids and families around. However, I think the Ritz is probably your best option for a higher end resort that is on the beach and will minimize exposure to families.
P.S. I believe the closest Four Seasons is located in Anguilla - a bit of a commute to San Juan <img src="http://www.traveltalkonline.com/forums/images/graemlins/Wink.gif" alt="" />.
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